The invention is directed to ventilating systems which may be utilized for handling heated or cooled air. In a typical system, a duct is connected to a furnace or air conditioning system, and distribution pipes are connected at intervals to the duct. This is accomplished by forming holes in the duct walls and providing collars whereby one side of the collars can be secured at the hole, and pipe sections then attached to the collars.
Collars of the type referred to are generally formed from strips of metal. Copending application Ser. No. 912,509, entitled Rotary Notcher and Former, illustrates equipment of a type which may be utilized for producing collars. That arrangement includes means for providing a notched edge on one side of a strip whereby tabs are formed. These tabs can then be bent back after this side of the collar is inserted in a duct hole whereby the collar will be secured in position.
The apparatus will also form a bead in the strip whereby the position of the collar relative to the duct hole can be accurately determined. Finally, the apparatus produces a crimped section along the opposite side of the strip. When the collar is formed and located in position, a pipe end can then be conveniently fit around this crimped section.
In utilizing formed strips of the type referred to, it is desirable to lock the opposite ends of the strip together whereby a collar of a desired configuration, for example rectangular or circular, will be achieved. By locking the strip ends together, it is also much easier to handle the collars when attaching them to a duct and when placing a pipe end in position.
Various lock designs have been utilized. In a typical design, the strip ends are bent to provide return portions and one can then be interlocked with the other by locating the respective return portions in a gripping relationship.